Are you planning to travel for business or pleasure? According to AARP, the best time to purchase airline tickets is Wednesday from midnight to 1:00 a.m. (in the time zone of the airline’s main hub or base (Delta is headquartered in Atlanta, GA and USAirways is in Tempe, AZ).
This time period is when most airline computer systems purge the reserved but not booked (paid)reservations.
Also, try to delete your internet cookies prior to searching and booking flights so that the airline website you are visiting thinks you are a new customer! These sites remember if you have shopped around, what you’ve looked at and how long you visited the site. As a general rule sites will reserve the best prices for new shoppers.